Acquiring the file lock when checking if the feeds are current can make
it appear as if an update is in progress, so the checks are first
performed before attempting to acquire the lock.

This makes it simpler to get the feed version from the scanner without
comparing it to the database version.

This way the main process is not blocked if part of the version check
like getting the VTs feed version from the scanner takes longer to
complete.

The feed type must be either "cert" or "scap" and the database check
must use the correct type.